Small hand-held radio transmitter and receiver devices are now used in many applications which have a loudspeaker to reproduce received signals and a microphone to translate speech into signals for transmission. Such units are subject to rough usage and there has been a problem in providing a microphone which is suitable for such use and which is protected from damage due to shock and from entry of foreign material. The microphone for such use must be quite small and may be a cartridge with a small input hole which is subject to being clogged by dirt, moisture, or other foreign material.
In such small portable devices, it is desired that a single grille be provided on the front of the housing through which sound produced by received signals is projected, and through which sound to be transmitted is applied to a microphone. Various arrangements have been used, such as the suspension of a microphone in front of a loudspeaker cone, but these have not been entirely satisfactory. It has also been proposed to use a combined loudspeaker microphone transducer, but there have been problems in providing the desired fidelity of operation in the two directions.